Circuit breaker



Nov. 4, 1958 D. B. ROBINSON 2,859,304

CIRCUIT BREAKER Filed July 9, 1954 2 Shuts-Sheet 1 INVENTOR. flower6231x307 D. B. ROBINSON CIRCUIT BREAKER Nov. 4, 1958 2 Sheets-Sheet 2Filed July 9, 1954 IN V EN TOR.

United States Patent CIRCUIT BREAKER Donald B. Robinson, Detroit, Mich.,assignor, by meene assignments, to I-T-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Application July 9,1954, Serial No. 442,304

9 Claims. (Cl. 200-116) This application relates to circuit breakers anddiscloses an improvement in the circuit breaker disclosed in Patents2,374,778, issued May 1, 1945, to E. T. Platz; 2,385,727, issuedSeptember 25, 1945, to E. T. Platz; and 2,487,725, issued November 8,1949, to E. T. PlatZ.

,These patents disclose a circuit breaker having a push button typeoperation, which may be manually operated successively for opening andclosing the circuit breaker contacts. The breaker is automaticallyoperable for opening the circuit breaker contacts upon the occurrence ofan overload current in the load circuit containing the breaker. Thebreaker includes in the operating mechanism a thermally responsive latchelement which is manually engageable with, and automatically andmanually disenga'geable from, a holding member in the mechanism. Theoverload rating of the breaker, i. e., the overload current value atwhich it is desired to have the circuit breaker open the circuitautomatically, is determined. by the degree of overlap of the latchportion of the thermally responsive latch element with the retainingportion of the holding member. Such circuit breakers are normallymanufactured with a predetermined overload rating established bycalibrating the breaker mechanism to obtain the appropriate degree oflatching overlap between the thermally responsive latch element and theholding member. However, it is desirable to permit this calibration tobe easily and quickly changed at times by an authorized person toincrease the overload rating of the circuit breaker and thereby permitthe load circuit to carry a higher value current when otherwise it wouldnot do so. Additionally, it may be desirable to temporarily increase thelatching overlap to thereby preclude release of the latch and separationof the contacts upon the occurrence of severe shock or mechanicalvibration, such as that occurring on a battleship during the firing ofthe armament.

Accordingly, a principal object of this invention is to provide acircuit breaker which permits an increase in the predetermined overloadrating.

Another object of this invention is to permit variation in the overloadrating of a circuit breaker only by an authorized person.

. Another object is to provide a circuit breaker in which the overloadrating can be varied without altering the operating characteristics ofthe breaker.

Another object is to provide a mechanism in a latch type circuit breakerwhich enables an authorized person to selectively prepare the breakerfor unusual shock or mechanical vibration.

Another object of this invention is to provide a circuit breaker inwhich the overload rating can be varied from the exterior of the circuitbreaker housing.

7 Still another object of this invention is to provide a circuit breakerin which the overload rating can be varied by a simple, inexpensivemechanism.

Still other objects and features of the invention will appear from thespecification and drawings in which:

Fig. 1 is an elevational view of a circuit breaker with the housingcover removed showing an embodiment of the invention disengaged from thecircuit breaker mechanism.

Fig. 2 is a partial elevational view of a portion of the circuit breakermechanism of Fig. 1 showing an embodiment of the invention engaged withthe circuit breaker mechanism.

Fig. 3 is a partial cross-sectional view as if on line 33 of Fig. 1.

Fig. 4 is a partial cross-sectional view as if on line 44 of Fig. 1.

Fig. 5 is a partial cross-sectional view as if on line 5-5 of Fig. 1.

Fig. 6 is a partial cross-sectional view as it on line 66 of Fig. 2.

Fig. 7 is an exploded view of the circuit breaker handle showing thecomponent parts of an embodiment of the invention.

Fig. 8 is an elevational view of the circuit breaker handle containing amodification of the embodiment of the invention shown in Fig. 1.

Fig. 9 is a bottom View of the handle shown in Fig. 8.

Referring to the drawings (Fig. 1), a circuit breaker, as disclosed inthe hereinabove mentioned patents, includes a casing 10 of moldedinsulating material with the cover removed. Extending through the rearwall of this casing 10 is a line connector (not shown), having securedthereto a fixed contact 11 and a load connector (not shown). Formed inthe rear wall of casing 10 are grooves (not shown) in which an operator12, comprising an embodiment of the invention which will be hereafterdescribed, is slidably disposed. These grooves, in conjunction with thecover of casing 10, serve to guide and position the operator 12 in itsinward and outward movement. Beneath operator 12, with one end extendinginto a recess thereof, is a handle return spring 14, the opposite end ofwhich is seated on an abutment extending from the rear wall of casing10. Also positioned below operator 12 and adjacent to the rear wall ofthe casing 10 (Fig. 1) and arranged to be engaged by an extension 15 ofthe operator 12 when the breaker mechanism is in the open circuitposition is a support member 16. Extension 15 upon inward movement ofoperator 12 engages extension 17 of support member 16 to prevent lateralmovement of support member 16 and imparts the operating force applied tooperator 12 to the circuit breaker mechanism. Support member 16 has acutout portion 18 which defines a latch surface 19. A composite member20, having a pivot pin 21, is journalled in an opening in the lowerportion of support member 16. This composite member 20 includes abimetallic latch 22 having a turned down latching hook 23, a fixedcontact 24, and a guide lug 25 which abuts the upper surface of supportmember 16 to thereby determine the degree of overlap of latching hook 23with latching surface 19 of cutout 18 of support member 16. A mainspringlug 26 receives one end of mainspring 27 which has the opposite endseated in the lower part of casing 10 at 28. Mainspring 27 providescircuit opening and circuit closing force upon actuation of the breakermechanism to these positions. Mainspring 27 also biases composite memberinwardly against support member 16 to the extent permitted by theengagement of guide lug 25 with the upper surface of support member 16when the circuit breaker is in the closed circuit position, shown inFig. 1.

Secured to the upper end of bimetallic latch member 22 is a flexibleconductor 29 which connects the latch member 22 with a load connector(not shown).

Referring now specifically to operator 12 (Figs. 2 and 7) whichcomprises a rear half 31, a front half 32, adapted to be securedtogether by bolts 33, which are inserted through holes 34 and fastenedby nuts 35. Rear half 31 and front half 32 are formed with recesses 36and 37, respectively, which form a key slot 38 (Fig. when the halves '31and 32 are assembled. Each recess is further concavely enlarged in thecenter to form a shaft opening 39 in key slot 38, as shown in Figs. 5and 6. Each recess is further cut away on alternate sides to formcamways 40 and 41, which incline downwardly and toward the centerline ofshaft opening 39 to recesses 40a and 41a in rear half 31 and front half32, respectively, as shown in Fig. 7. The middle portion of front half32 is cut away to leave a stud 51 and a wall 52 which abut surface 53 at54 and 55, respectively. 1 The lower portion of rear half 31 includes acam surface 59which functions to actuate the breaker mechanism fromclosed circuit position to open circuit position, as described below. Achamber 56 (Fig. 4) is thus formed when rear half 31 and front half 32are assembled. Disposed within this chamber is an overload latch 60 andan overload latch spring 71 (Fig. 7). Overload latch 60 is preferablymade of insulating material and comprises an L-shaped member having abody portion 61, a leg 62 of less thickness than the body portion, and apivot 63. Body portion 61 is beveled as shown in Fig. 7 to form a camsurface 64. Overload latch spring 71 is preferably constructed of springsteel formed in a U shape and having an upper leg 71a and a lower leg71b.

A journal hole 56 is provided in the front half 32 of operator 12 toreceive pivot 63 of overload latch 60.

Operator 12 is assembled by positioning overload spring 71 around bodyportion 61 of overload latch 60 with the lower leg 71b abutting surface61a of latch 60. Pivot 63 is then placed in journal 56 of the front half32 of operator 12 and the upper leg 71a of overload latch spring 71positioned outside lug 51 (Fig. 1). The rear half 31 and front half 32are then secured together by bolts 33 and nuts 35.

To actuate overload latch 60 to increase the overload rating of thebreaker, a key 82 is provided (Figs. 1 and 2). Key 82 is formed from astrip of metal, preferably steel, and comprises a handle 81 of circularshape, a shaft 82a having fiat wing-like extensions 83a projectinglaterally from the end (Fig. 6).

With overload latch 60 disengaged and the circuit breaker in the closedcircuit position of Fig. 1 with key 82 removed, the breaker operates asfollows: Upon manual actuation of operator 12, cam surface 59 of therear half of operator 12 strikes latch hook 23 of bimetallic latch 22and cams it outwardly to release latch book 23 from engagement withlatch surface 19.

Composite member 20, upon release of latch hook 23, rotatescounterclockwise about pivot 21 under the bias of mainspring 27 toseparate movable contact 24 from fixed contact 11. Support member 16moves to the right to position extension 17 beneath extension 15 ofoperator 12. To move the circuit breaker to the closed circuit position,operator 12 is again manually depressed, forcing support member 16downwardly and rotating composite member 20 clockwise about pivot 21until latch hook 23 engages behind latching surface 19 under the inwardbias of mainspring 27. Upon release of operator 12, support member 16moves upwardly and to the left to the position of Fig. 1, permittingcomposite member 20 to move upwardly under the bias of mainspring 27 tobring movable contact 24 and fixed contact 11 together.

Upon the occurrence of an overload current of suificient magnitude,bimetallic latch 22 is heated to warp outwardly to release latch hook 23from latching surface 19 of support member 16. The degree of overlap oflatch hook 23 with latching surface 19 thus determines the overloadrating of the breaker as it determines the extent to which bimetalliclatch 22 must warp to release latch hook 23 from latching surface 19 4and permit the breaker to move to the open circuit position.

If it is desired to increase the overload rating of the circuit breakeror prepare the breaker for shock, key 82, which is in possession of anauthorized person, is inserted into slot 38 of operator 12 (Fig. 1) intoabutment with cam surface 64 of overload latch 60 (Fig. 3). Key 82 isthen turned counterclockwise. Extensions 83a of shaft 82a then followcamways 41 causing key 82 to move downwardly. The end of shaft 82a ofkey 82 forces overload latch 60 to rotate counterclockwise against thebias of spring 71 about pivot 63. Further rotation of key 82 to theposition of Fig. 2 causes leg 62 of overload latch 60 to position itselfabove support member 16 and adjacent to latch hook 23 of bimetalliclatch 22. Extensions 83a engage recesses 40a, 41a to maintain key 82 andoverload latch 60 in this position.

Upon the occurrence of the rated overload, latch hook i 23 will bereleased from latchsurface 19 of support member 16 upon the warping ofbimetallic latch 22 and will strike the inner surface of leg 62 ofoverload latch 66. Movement of the circuit breaker mechanism to the offcircuit position is thus prevented. Greater overload will causeadditional warping of bimetallic latch 22 to permit latch hook 23 toclear leg 62 of overload latch 60. The particular additional overloadrating desired to be imposed on the circuit breaker can thus becontrolled by varying the thickness of leg 62 of overload latch 60. Ifthe breaker is subjected to severe shock or mechanical vibration,sufficient to' release latch hook 23 from latch surface 19, opening ofthe breaker will also be prevented by overload latch 60.

When it is desired to have the circuit breaker function i normally, key82 is rotated clockwise to remove extension 83a from recesses 40a,41a'of operator 12 and permit overload latch 60 to rotate clockwiseabout pivot 63 under the bias of spring 71 to the disengaged position ofFig. 1. Key 82 is then withdrawn and the circuit breaker will functionas originally calibrated.

Disclosed in Figs. 8 and 9 is another embodiment of the invention. Inthis embodiment an operator comprises a unitary housing having disposedin a chamber formed therein overload latch 62 formed as in the preferredembodiment and a torsion spring 92. A pivot pin 93 is positioned inhousing 91 and journals overload latch 62. Torsion spring 92 ispositioned on pivot pin 93 and has one leg secured in a recess 94 and aright angle portion of the other leg positioned beneath the body portionof overload latch 62, as shown in Fig.9. A slot 95 is cut through thetop wall of housing .91 .to permit the insertion of key 82. Theoperation of'this embodiment to vary the overload rating of the circuitbreaker is the same as in the preferred embodiment.

Now having described the invention, reference should be had to theappended claims for the scope thereof.

I claim: a I i 1. In a thermal overload circuit breaker having a casing,a fixed contact, an operator slidably disposed in said casing, amechanism including a support member actuable by said operator, acomposite member actuable by said support member, said compositemember'including-an electroresponsive latch element engageable with, anddisengageable from, said support member upon successive operation ofsaid operator, said operator including means engageable with saidmechanism for selectively varying the predetermined overload rating ofsaid circuit breaker, said operator comprising mating halves having achamber to receive said means when disengaged from said mechanlsm.

2. In a thermal overloadcircuit breaker having a casing, a fixedcontact, an operator slidably disposed in said casing, a mechanismincluding a support member actuable by said operator, a composite memberactuable. by said support member, said composite member including anelectroresponsive latch element engageablewith, and disengageable from,said support member upon successive operation of said operator, saidoperator including means engageable with said mechanism for selectivelyvarying the predetermined overload rating of said circuit breaker, saidmeans including a resilient element, an overload latch biased thereby toremain in disengaged position, and an actuator insertable in saidoperator and engageable with said overload latch to thereby cause saidoverload latch to position itself in said mechanism.

3. In a thermal overload circuit breaker having a casing, a fixedcontact, an operator slidably disposed in said casing, a mechanismincluding a support member actuable by said operator, a composite memberactuable by said support member, said composite member including anelectroresponsive latch element engageable with, and disengageable from,said support member upon successive operation of said operator, saidoperator including means engageable with said mechanism for selectivelyvarying the predetermined overload rating of said circuit breaker, saidoperator comprising mating halves having a chamber to receive said meansWhen disengaged from said mechanism, said means including a resilientelement, an overload latch biased thereby to remain in disengagedposition, and an actuator insertable in said operator and engageablewith said overload latch to thereby cause said overload latch toposition itself in said mechanism.

4. For use with a circuit breaker, a variable overload mechanismincluding a resilient member, an overload latch member biased thereby toremain in a first position, an actuator engageable with said overloadlatch member to thereby actuate said overload latch member to a secondposition, a latch means engageable with said actuator to latch saidoverload latch member to said second position against the force of saidresilient member, said resilient member causing said overload latchmember to return to said first position upon disengagement of saidactuator from said overload latch member.

5. For use with a circuit breaker, a variable overload mechanismincluding a manual operator having a chamber formed therein, an overloadlatch member and a resilient member disposed in said chamber, saidresilient member biasing said overload latch member to remain in a firstposition, an actuator insertable into said operator to engage saidoverload latch member to thereby actuate said overload latch member to asecond position, said resilient member causing said overload latchmember to return to said first position upon disengagement of saidactuator from said overload latch member.

6. For use with a circuit breaker, a variable overload mechanismincluding a manual operator having a chamber formed therein, an overloadlatch member and a resilient member disposed in said chamber, saidresilient member biasing said overload latch member to remain in a firstposition, an actuator insertable into said operator to engage saidoverload latch member to thereby actuate said overload latch member to asecond position, said resilient member causing said overload latchmember to return to said first position upon disengagement of saidactuator from said overload latch member, said manual operatorcomprising a first half and a second half, each half havingcomplementary cam formations to form a camway to cause said actuator tomove downwardly to move said overload latch member upon rotation of saidactuator in said operator.

7. In a thermal overload circuit breaker having a manual operator, abimetallic latch member, retaining means engageable by said latch memberto maintain said circuit breaker in a closed circuit condition, saidbimetallic latch member warping upon rated overload to free itself fromsaid retaining means to permit said circuit breaker to move to the opencircuit position, and means disposed in said manual operator andactuable from without said circuit breaker to move said means adjacentto said latch member to thereby selectively increase said overloadrating of said circuit breaker.

8. A thermal overload circuit breaker being comprised of a pair ofcooperating contacts, a casing, an operator, a support member, acomposite member, an actuator; one of said cooperating contacts beingsecured to said casing; said operator being slidably mounted in saidcasing; said support member being actuable by said operator; saidcomposite member being actuable by said support member; said compositemember including the other of said cooperating contacts and anelectroresponsive latch element engageable with, and disengageable from,said support member upon successive operations of said operator; saidoperator including a resilient element, an overload latch and a chamber;said overload latch being disposed in said chamber when biased to aninoperative position by said resilient element; said actuator beinginsertable in said operator and engageable with said overload latch toposition said overload latch adjacent to said electroresponsive latchelement and thereby increase the rating of said circuit breaker by apredetermined amount.

9. In a thermal overload circuit breaker having a casing, a fixedcontact, an operator slidably disposed in said casing, a mechanismincluding a support member actuable by said operator, a composite memberactuable by said support member, said composite member including anelectroresponsive latch element engageable with, and disengageable from,said support member upon successive operation of said operator, saidoperator including means engageable with said mechanism for selectivelyvarying the predetermined overload rating of said circuit breaker, saidoperator comprising mating halves forming a chamber and a recess, saidchamber receiving said means when disengaged from said mechanism, saidmeans including a resilient element, an overload latch biased thereby toremain in disengaged position, and an actuator insertable in saidoperator and engageable with said overload latch to thereby cause saidoverload latch to position itself in said mechanism, one end of saidactuator being received by said recess and latched therein by the forceof said resilient element when said means is in engagement with saidmechanism; said actuator serving as an indicator for the position ofsaid overload latch.

References Cited in the file of this patent UNITED STATES PATENTS1,078,156 Locher Nov. 11, 1913 1,457,310 Livingston June 5, 19231,725,518 Hodgkins Aug. 20, 1929 2,156,761 Jackson et al. May 2, 19392,385,727 Platz Sept. 25, 1945 2,571,812 Armstrong et al. Oct. 16, 19512,633,515 Locher Mar. 31, 1953 2,639,349 Ingwersen May 19, 19532,694,122 Ingwersen Nov. 9, 1954 2,726,299 Carlson Dec. 6, 1955

